Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes) - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 38 (permalink) Old 07-09-2012, 02:55 PM Thread Starter
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Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

Like many of you, I read all the info on the benefits of running the large rear sway bars on Stock vehicles. Many touted the beneficial values of reducing wear on front tires, increasing rear rotation, and when all was said and done, faster times.

To those of you who are running a larger rear bar, what actual effects are you experiencing, before compared to after?

I'm running the Corksport three position 32mm rear bar. I've had it in all three positions at different events, and I keep records comparing my raw times vs consistent other local drivers (my "Benchmarks&quot to try to gauge progress. Given the nature of different course designs, and in my case, two different venues (one smaller & tighter, one more open and longer/faster), it is not always possible to have a direct correlation, but across time averages can be drawn.

In my case, I'm not seeing a huge gain from using this rear bar; and I'm not sure it's any faster than the stock rear bar (I have an '08 S Hatchback in H Stock Street Tire).

What are some other experiences out there?

One thing I've noticed is that with the stock rear bar, I get about 1" of inside rear wheel lift in a hard corner. With the large rear bar I'm getting about 3" to 4" of inside rear wheel lift. I'm wondering that since stock I get the rear lift, if the large bar just creates an excess, thus no additional handling gain. Like a point of diminishing return, as it were.

Please discuss and share what you've experienced.

Scott Meyers
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post #2 of 38 (permalink) Old 07-09-2012, 04:02 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

Same bar here (Corksport). Definitely think the benefits are not as great as seem people would like you to believe. I think there is some benefit though (mainly more neutral handling and perhaps slightly less wheelspin though the effect is minimal at best).

What I've noticed more than anything is the change in PAX for HS this year. Last year it was .791, this year it is .799. What that means is you have to be a full .5 sec faster on a 60 sec course to achieve the same pax time as last year. I believe HS had the 4th highest pax increase from 2011 to 2012. If you feel the sway bar isn't making the car faster compared to last year, the pax change is probably counteracting the advantage of running it and then some. I autocross with the STL region quite often and talk to Rick Ruth (the creator and administrator of the pax system) and he openly admits that .791 was quite a gift to HS last year. It's just plain tougher to pax well this year in HS compared to last year.
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post #3 of 38 (permalink) Old 07-09-2012, 04:19 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

Disclaimer: I ran my car in HS from Nov 2007 to May'ish 2010, so I never had a chance to change the rear bar.

With that said, if I ran HS, I would stick with the stock bars. When front grip was good, I never had a problem with rotation. Unloading the inside rear earlier and putting more load on the outside front is going to make the car inconsistent at best and more likely to go on 2 wheels at worst.

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post #4 of 38 (permalink) Old 07-09-2012, 04:37 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

I don't have any real quantitative data, but I liked how my car handled a lot better with the Mazdaspeed3 stock front bar on it (I'm an '04 sedan S) and stock rear bar. Seemed like the tire wear was significantly better with it on there, and it really didn't hurt rotation much. I always thought the car rotated quite well. I actually like how it handles now better than when I was (poorly) set up for ST class with my intake and progress rear bar (and stock front bar). I never tripoded my car with the front bar, at least not that I noticed that much, but I wasn't on Hoosiers (I was on Hankook Z214 C71's). I also had koni SA's, which made a MUCH bigger difference than anything having to do with the sway bar.

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post #5 of 38 (permalink) Old 07-09-2012, 04:39 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

[quote author=steverife link=topic=211373.msg4247719#msg4247719 date=1341865153]
more likely to go on 2 wheels at worst.
[/quote]

I'm pretty sure Steve was working the course when I two wheeled the car in his section at the Blytheville Pro? Went in too fast and aggressive in a set of heavily offset gates and she was definitely up on two. That being said, it's been on two a couple times before on the stock bar as well, but of course that is over hundreds of autocross runs on race rubber.


As Steve said, I think the RSB transfers load faster to the outside front making it easier to pick up the inside rear, but maximum weight transfer would be the same I'd imagine once that inside rear gets in the air.
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post #6 of 38 (permalink) Old 07-09-2012, 08:18 PM Thread Starter
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

First, thanks for all the comments.

Now, look at this......(large rear bar)...

Compare to this.......(stock rear bar)...

My thinking is that once that rear tire is off the ground, that anything higher is....... unnecessary. I think that's what Adam said. Add to that, looking at the more
severe front suspension angle, seems like it might be actually hurting effective front camber too. :shock:

I'm on RS3 street tires; I can get the rear up 1"-2" with the stock bars in a severe corner. I'm thinking the large rear bar ain't helping me. And to be clear,
not just the Corksport, I mean with ANY large rear bar.

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post #7 of 38 (permalink) Old 07-09-2012, 08:28 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

^^^^^^^^^^^^

This is the reason a rear bar only on a FWD car is a waste of time. Once that inside tire is unloaded, the rear bar is worthless.

Maximize front grip - eventually you will have enough front grip that the rear will have less and start to rotate for you. Alignment also helps here as well. Like Steve, I don't have any problem with getting the rear to move around for me and that is running with stock swaybars.

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post #8 of 38 (permalink) Old 07-09-2012, 09:00 PM Thread Starter
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

[quote author=PZ link=topic=211373.msg4247775#msg4247775 date=1341880103]
Maximize front grip - eventually you will have enough front grip that the rear will have less and start to rotate for you. Alignment also helps here as well.
[/quote]
Interesting. Please elaborate on what else can be done in Stock to maximize front grip. We all know that more negative front camber is out of the question ,
so what have the rest of you done to achieve this? What "alignment" settings specifically?

Side note to the big rear bar effects in my world; It did NOT help me to rotate the car any more.

Second "curiosity"; might a slightly larger FRONT bar actually help achieve more front grip on these Mazdas?

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post #9 of 38 (permalink) Old 07-09-2012, 09:09 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

[quote author=mazda3az link=topic=211373.msg4247783#msg4247783 date=1341882011]

Interesting. Please elaborate on what else can be done in Stock to maximize front grip. We all know that more negative front camber is out of the question , [/quote]

Big ass tires (245's are the minimum entry point.)
Big ass sway bar (which I don't have but should have)


[quote author=mazda3az link=topic=211373.msg4247783#msg4247783 date=1341882011] What "alignment" settings specifically? [/quote]

I run about 3/16" total toe out in the rear. Just enough to be technically 'in spec' and keeps tire wear to acceptable levels. I could probably run a little more, but tire wear (street tires) would be unacceptable.

[quote author=mazda3az link=topic=211373.msg4247783#msg4247783 date=1341882011]

Second "curiosity"; might a slightly larger FRONT bar actually help achieve more front grip on these Mazdas?
[/quote]
Yes, because you keep more of the tire on the ground. You may experience more wheelspin, but your speed coming out of sweepers will be higher.

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post #10 of 38 (permalink) Old 07-09-2012, 10:07 PM
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Re: Actual Effects of Running Large Rear Sway Bars in Autocross (Stock Classes)

I'm not a believer in the front bar either. I always felt that car's #1 weakness was wheelspin and #2 was vague turn-in. I wouldn't want to do anything to make #1 worse.

I REALLY liked my car in sweepy stuff. My next step was pimpy shocks so I could try to run a lot of compression up front. ...and maybe try some endlinks with the stock front bar.

Of course, it is hard to justify that sort of money on an HS car, so I decided to run STS.

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